The present invention relates to a method of making an ejector tube for molds in general, though it is intended for application in particular with injection mold. The method is based on a series of stages of work carried out on a length of tubing of suitable length and diameter so as to achieve, through the minimum number of operations, the shaping of the ejector tube which serves as the guide for the ejectors used in molds, with both the ejector tube and the ejector being held in place by a fixing head.
The ejector tubes used as guides for ejectors linked to their fixing heads and included in injection moulds are conventionally produced from a bar or rod which is subjected to a series of processes: first, one of the ends is worked to produce the head, which is oversized with respect to the rest of the body; next, an axial bore is cut all the way through, and then suitably machined to give two diameters; it is then trued, and further operations are performed until the ejector tube sought is obtained.
The producing the ejector tube in the conventional manner, the starting point is a solid bar which, since its bore has to be drilled out, entails a loss of material, and furthermore this bar initially is very heavy. For example, to produce a standard ejector tube measuring 400 mm in length with a bore diameter of 8 mm and an outside diameter of 12 mm, the starting point is a bar of metal whose total weight is approximately 1,290 grams.
Furthermore, special machine tools are needed to produce it. As a consequence of all this, fourteen to sixteen different operations have to be performed--a long and laborious process.
It must also be borne in mind that, since material has to be removed to produce the bore, molecules will be broken, thereby reducing elasticity in the mechanical strength of the end product.
Another physical problem which cannot be eliminated arises during the heat treatment, since the various molecular masses which make up the product have varying thicknesses, and this makes the cooling stage in the hardening fragile, plastic deformations arising which require a special, additional truing process.
Finally, it must be pointed out that, in conventionally produced ejector tubes, when the tube has to be cut to length, the cut has to be made at the upper end, since naturally this operation is performed after attaching the piece to the appropriate fixing head. Since this area of the piece is the one in which the ejector and the tube itself are close-fitted, and since the cutting reduces the size of this area, that close-fit quality is lost.